An airplane is moved by several turbojet engines each housed in a nacelle also housing a set of connected actuating devices related to its operation and performing various functions when the turbojet engine is operating or stopped. These connected actuating devices in particular include a mechanical thrust reverser system.
More specifically, a nacelle generally has a tubular structure comprising an air intake upstream of the turbojet engine, a middle section intended to surround a fan of the turbojet engine, a downstream section housing the thrust reverser means and designed to surround the combustion chamber of the turbojet engine, and generally ends with a jet nozzle whereof the outlet is situated downstream of turbojet engine.
Modern nacelles are intended to house a dual flow turbojet engine capable of generating, by means of the rotating fan blades, a flow of hot air (also called primary flow) coming from the combustion chamber of the turbojet engine, and a flow of cold air (secondary flow) that circulates outside the turbojet engine through an annular channel, also called tunnel, formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two flows of air are ejected outside the turbojet engine through the back of the nacelle.
The role of a thrust reverser is, during the landing of an airplane, to improve the braking capacity thereof by reorienting at least part of the thrust generated by the turbojet engine forward. In this phase, the reverser obstructs the annular channel of the cold air flow and orients that flow toward the front of the nacelle, thereby generating a counter-thrust that is added to the braking of the wheels of the airplane.
The means used to perform this reorientation of the cold air flow vary depending on the type of reverser. However, in all cases, the structure of a reverser includes movable cowls that can be moved between a deployed position on the one hand, in which they open a passage in the nacelle intended for the deflected flow, and on the other hand, a retracted position in which they close that passage. These cowls can perform a cascade function or simply activate other cascade means.
In the case of a cascade thrust reverser, also called a cascade reverser, the reorientation of the flow of air is done by cascade vanes associated with reverser flaps, the cowl serving simply to slide so as to uncover or cover the cascade vanes. The reverser flaps form blocking doors activated by the sliding of the cowling generally creating closing of the annular channel downstream of the vanes so as to optimize the reorientation of the cold air flow.
Generally, the cascade vanes 1 are attached to the case of the turbojet engine and the middle section of the nacelle using a stub frame 3 (see FIG. 1). The typical stub frames 3 comprise a multitude of parts, some of which are made from a composite material, and others of which are made from a metal material.
More specifically, a typical stub frame 3 comprises a front panel 5 intended to secure the middle section of the nacelle to a structural element 7 called “conical shell” belonging to the stub frame 3. Said structural element 7 enables fire resistance. The stub frame 3 also comprises a cascade edge element 9 ensuring the aerodynamic line. The front ring panel 5 and the structural element 7 are fastened together.
An inner ring 11 makes it possible to fasten one end of the structural element 7 and one end of the cascade edge element 9. Said inner ring 11 also makes it possible to fasten the stub frame 3 to the case of the turbojet engine by means of an attached piece 15. An outer ring 17 makes it possible to fasten the structural element 7, the cascade vane 1, and the cascade edge element 9.
The stub frame 3 also comprises stiffeners (not shown).
Generally, the stiffeners, the inner ring 11, and the outer ring 17 are made from a metal material.
The stub frame 5, the structural element 7, and the cascade edge element 9 are made from a composite material.
The number of parts necessary to form a stub frame as well as the use of different types of materials make the manufacture and installation of said stub frame complex.
There is therefore a need to provide a stub frame for a nacelle that makes it possible to reduce the mass, production costs, and head losses.